Motorized sled for stair chairs

ABSTRACT

A lightweight motorized and tracked sled for attachment to a variety of stair chairs is described. A power supply or power source provides power to a motor driving a track configured to engage a set of stairs. The motor and track can lift and support the stair chair and a patient thereon up or down one or more flights of stairs. The track driven by the motor has a length sufficient to simultaneously engage the lips or edges of a pair of sequential steps, but may be otherwise limited in length to reduce the weight of the track. To ensure that the sled and attached stair chair are stably supported while ascending or descending stairs, the sled may have rails, skis, or passive tracks having a length sufficient to ensure that the rails, skis, or passive tracks are always over the edge or lip of no fewer than two steps.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser.No. 61/093,162, filed Aug. 29, 2008 in the names of Nathan R.Walkingshaw and Mark Wenzel and titled “Motorized Sled for StairChairs.”

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to stair chairs, and more particularly toa motorized sled for attachment to stair chairs to convert stair chairsinto powered stair chairs for power-assisted stair ascents and descents.

2. Background and Related Art

Stair chairs are commonly used to maneuver patients in a variety ofsituations. Such situations include emergency response situations andevacuations of multi-level buildings. Stair chairs are typicallydesigned to permit rolling movement of a patient or evacuee over flatsurfaces and carrying of the stair chair up or down flights of stairs orover rough surfaces. Manufacturers of such chairs include StrykerCorporation of Kalamazoo, Mich. and Ferno-Washington, Inc. ofWilmington, Ohio. An illustrative stair chair 10 is shown in perspectiveview in FIG. 1.

The stair chair 10 includes rear bearings, typically wheels or casters12, which permit the stair chair 10 to be rolled across a flat surface.In some stair chairs, no front wheels or casters are provided, and toroll the stair chair 10 across a surface, the user is expected to tipthe stair chair 10 backward slightly until substantially all the weightof the stair chair 10 and a patient or evacuee thereon is over the rearwheels 12. In other instances, the stair chair 10 is provided with frontcasters 14, which permits rolling of the stair chair 10 without anytipping. The rear wheels 12 and the front casters 14 (if any) aretypically attached to a chair frame 16. The chair frame 16 providesvarious support elements to support a patient or evacuee, such as a footrest 18, a seat 20, and a back 22. For convenience in describing thestair chair 10, the chair frame 16 has been illustrated without anypadding elements or other support surfaces for the seat 20 and the back22.

The stair chair 10 may fold, such as at hinges 24, to make the stairchair 10 more compact for storage. The stair chair 10 may also beprovided with handles 26 to assist responders in carrying the stairchair 10 up or down stairs or in otherwise moving the stair chair 10.The handles 26 nearest the foot rest 18 may be extendable so theresponders or other users may more easily carry the stair chair 10 up ordown stairs. When carried by the handles 26, the stair chair 10 istypically tipped back slightly so that the user at the foot of the stairchair 10 may stand upright while carrying the stair chair 10.

Stair chairs 10 are very useful in evacuating or otherwise movingpatients or other people unable to move on their own. In a typical usesituation, a patient is loaded onto the stair chair 10 (when the stairchair 10 is in its fully-unfolded state), the stair chair 10 is wheeledto the head or foot of a flight of stairs, and the stair chair 10 isthen carried by two or more persons down or up the flight of stairs.Once any stairs have been navigated, the stair chair 10 is then wheeledfurther, either to additional stairs, to an ambulance, or to some otherlocation where the patient is removed from the stair chair 10. Stairchairs 10 are often used in emergency situations where elevator servicehas been interrupted, is unavailable, or is inadvisable.

BRIEF SUMMARY OF THE INVENTION

Implementations of the invention provide a motorized and tracked sledfor attachment to a stair chair to thereby reduce the effort needed tooperate a stair chair when ascending or descending stairs or other morechallenging terrains. The sled may be lightweight and may be adapted forconnection to a variety of currently-existing stair chairs or may beadapted for future stair chair designs. In some implementations, thesled may be removably attached to the stair chair, and may be removedfor storage or when the sled is not being used in conjunction with thestair chair. The sled may include a power supply or power source, suchas a battery or battery pack, that may be attached to the sled or thatmay be separately carried to reduce the on-chair weight of the sled. Thepower supply or power source provides power to a motor driving a trackconfigured to engage a set of stairs. The motor and track may havesufficient power, torque, etc. to lift the stair chair and a patientthereon up one or more flights of stairs, and may also be used in apowered sense while descending stairs.

The track driven by the motor has a length sufficient to simultaneouslyengage the lips or edges of a pair of sequential steps. Additionally,the track belt may be provided with teeth, grooves, or other features tomore securely engage the steps of the stairway. Although the track issufficiently long to simultaneously engage the lips or edges of twosequential steps, the track may be otherwise limited in length to reducethe weight of the track. Therefore, to ensure that the sled and attachedstair chair are stably supported while ascending or descending stairs,one or more rails, skis, or passive tracks may be provided on the sled.While the track is of a length to simultaneously engage two sequentialsteps, the rails, skis, or passive tracks may have a length sufficientto ensure that the rails, skis, or passive tracks are always positionedso as to be over the edge or lip of no fewer than two steps. In otherwords, the rails, skis, or passive tracks may have a length sufficientto simultaneously be positioned over the edges of at least threesequential steps.

The sled may be configured so as to be able to fold up against the stairchair when the sled is not in use, to permit the stair chair to be moreeasily pushed across flat surfaces using the stair chair's wheels. Thesled may be sufficiently light-weight to permit the stair chair to becarried in a fashion currently common with stair chairs even when thesled is attached to the stair chair. Such carrying may occur when thesled is folded up against the chair in a stowed position. When the sledis in a deployed position, it may have any desired angle relative to theback of the stair chair, and such angle may be chosen to match the angletypically found in stair chairs being carried.

In some implementations, the sled essentially forms a single unit thatis removably attached to the stair chair. In other implementations, thesled is formed from readily-separable parts that may form separatefunctional units. For example, the sled may be formed from two units,the first unit being a powered track unit that serves a function ofproviding powered movement up and/or down stairways, and the second unitbeing a non-powered frame that serves a function of permittingnon-powered stair-contacting movement up and/or down stairways. Suchembodiments may be useful for reducing total weight of the stair chairand sled unit when ascending stairs and/or for separating portions ofthe stair chair and sled unit to maximize power supply life duringextended use periods.

These and other features of the implementations of the invention willbecome clear through practice of the implementations of the inventionand through the following description and appended drawings, which areincorporated by reference. The foregoing and following description isnot intended to be limiting, and the scope of the invention should bedetermined by reference to the claims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The objects and features of the present invention will become more fullyapparent from the following description and appended claims, taken inconjunction with the accompanying drawings. Understanding that thesedrawings depict only typical embodiments of the invention and are,therefore, not to be considered limiting of its scope, the inventionwill be described and explained with additional specificity and detailthrough the use of the accompanying drawings in which:

FIG. 1 is a perspective view of a prior-art stair chair;

FIG. 2 is a perspective view of a motorized sled attached to a stairchair;

FIG. 3 is a side view of a motorized sled attached to a stair chair;

FIG. 4 is a perspective view of a motorized sled attached to a stairchair in a stowed position;

FIG. 5 illustrates engagement of a motorized sled with a flight ofstairs;

FIG. 6 illustrates engagement of a motorized sled with a flight ofstairs;

FIGS. 7-11 illustrate features of a representative continuous track beltfor use with embodiments of the invention;

FIG. 12 is a perspective view of an alternate embodiment of a motorizedsled;

FIG. 13 is a perspective view of the embodiment of FIG. 12 with amotorized track portion separated from the remainder of the sled;

FIG. 14 is a perspective view of the embodiment of FIG. 12 with themotorized track attached to the sled and with the sled attached to astair chair; and

FIG. 15 is a perspective view of the embodiment of FIG. 12 with themotorized track removed from the sled with the sled attached to thestair chair.

DETAILED DESCRIPTION OF THE INVENTION

A description of embodiments of the present invention will now be givenwith reference to the Figures. It is expected that the present inventionmay take many other forms and shapes, hence the following disclosure isintended to be illustrative and not limiting, and the scope of theinvention should be determined by reference to the appended claims.

Embodiments of the invention provide a motorized and tracked sled forattachment to existing stair chairs. The sled may be lightweight and maybe adapted for connection to a variety of currently-existing stairchairs or may be adapted for future stair chair designs. In someembodiments, the sled may be removably/readily-reversibly attached tothe stair chair, and may be removed for storage, for when the sled isnot being used in conjunction with the stair chair, or when it isdesired to move the stair chair in a lighter-weight configuration. Thesled may include a power supply or power source, such as a battery orbattery pack, that may be attached to the sled or that may be separatelycarried to reduce the on-chair weight of the sled. The power supply orpower source provides power to a motor driving a track configured toengage a set of stairs. The motor and track may have sufficient power,torque, etc. to lift the stair chair and a patient thereon up one ormore flights of stairs, and may also be used in a powered sense whiledescending stairs.

The track driven by the motor has a length sufficient to simultaneouslyengage the lips or edges of a pair of sequential steps. Additionally,the track belt may be provided with teeth, grooves, or other features tomore securely engage the steps of the stairway. Although the track issufficiently long to simultaneously engage the lips or edges of twosequential steps, the track may be limited in length to reduce theweight of the track. Therefore, to ensure that the sled and attachedstair chair are stably supported while ascending or descending stairs,one or more rails, skis, passive tracks, or other stair-engagingportions, may be provided on the sled. While the track is of a length tosimultaneously engage two sequential steps, the rails, skis, passivetracks, or other stair-engaging portions may have a length sufficient toensure that the rails, skis, passive tracks or other stair-engagingportions are always positioned so as to be over the edge or lip of nofewer than two steps. In other words, the rails, skis, passive tracks,or other stair-engaging portions may have a length sufficient tosimultaneously be positioned over the edges of at least three sequentialsteps.

The sled may be configured so as to be able to fold up against the stairchair when the sled is not in use, to permit the stair chair to be moreeasily pushed across flat surfaces using the stair chair's wheels. Thesled may be sufficiently light-weight to permit the stair chair to becarried in a fashion currently common with stair chairs even when thesled is attached to the stair chair. Such carrying may occur when thesled is folded up against the chair in a stowed position. When the sledis in a deployed position, it may have any desired angle relative to theback of the stair chair, and such angle may be chosen to match the angletypically found in stair chairs being carried.

In some embodiments, the sled essentially forms a single unit that isremovably attached to the stair chair. In other embodiments, the sled isformed from readily-separable parts that may form separate functionalunits. For example, the sled may be formed from two units, the firstunit being a powered track unit that serves a function of providingpowered movement up and/or down stairways, and the second unit being anon-powered frame that serves a function of permitting non-poweredstair-contacting movement up and/or down stairways. Such embodiments maybe useful for reducing total weight of the stair chair and sled unitwhen ascending stairs and/or for separating portions of the stair chairand sled unit to maximize power supply life during extended use periods.

In at least one embodiment, the sled includes a motorized trackconfigured to engage steps of a staircase and a first stair-engagingportion configured to at least intermittently contact steps of thestaircase while the motorized track is engaging steps of the staircase.In some embodiments, the motorized track includes a continuous trackportion. The continuous track portion may include teeth to engage stairsor another surface, or it may be made of a soft material to engagestairs or another surface. The continuous track may loop around one ormore pulleys as well as a drive gear operative connected to a motor. Themotor is powered by a power supply, which may include a battery (whetherfixed or removable/replaceable) or a plug or wire connected to anexternal power source.

While some embodiments include only a first stair-engaging portion,other embodiments include two or more stair-engaging portions. Where twostair-engaging portions are present, they may be located on oppositesides of the motorized track. In some embodiments, the stair-engagingportions are elongate portions or members, so they can contact or beover the edges of multiple steps of a stairway simultaneously. Thestair-engaging portion or portions may include rails, skis, passive(non-motorized) tracks (with or without one or more brakes or brakesystems) that may include continuous tracks, or any other member thatsufficiently engages the steps of the stairway at least intermittentlyto stabilize the stair chair/sled as the steps are being ascended ordescended. Each stair-engaging portion or portions may have a long axisthat is substantially parallel to a long axis of the motorized track.

Where the stair-engaging portion (or portions) is a rail, ski, orsimilar structure, it may include a substantially-planar portion forresting on the steps. It may also include an upturned portion on one orboth ends to facilitate moving the rail, ski, or similar structure overthe edge of a next step of the staircase. The rail, ski, or similarstructure may include or be faced with a high-durability, low-frictionmaterial at least on a step-contacting surface of the rail, ski, orsimilar structure. Such materials include, for example, ultra-highmolecular weight polyethylene, high density polyethylene,polytetrafluoroethylene, and polyfluoroethylene. Where thestair-engaging portion (or portions) is a passive track, the passivetrack may include similar substantially-planar and upturned portionsdefined by at least a portion of the path of the track.

To ensure that the motorized track securely engages the steps of thestairway, at least a portion of the motorized track may extend step-wardor stair-ward past a stair-ward-most portion of the stair-engagingportion or portions. Thus, even when the stair-engaging portion orportions is/are contacting the edges of the steps, the motorized tracksecurely engages the edges of one or more steps at all times. Themotorized track may extend stair-ward past the stair-engaging portions adistance between approximately 0.5″ to 0.7″ (approximately 13 mm to 18mm), or approximately 0.6″ (approximately 15 mm). The portion extendingstair-ward past the stair-engaging portions may include one or moreteeth of a continuous track.

The motorized track may have a length sufficient to ensure that themotorized track is capable of simultaneously engaging the edges of atleast two sequential steps of a representative stairway, such as astairway of maximum-anticipated step spacing. This ensures that during astairway ascent or descent, the motorized track is always engaged withat least one step. This prevents situations where the stair chair couldbegin to slide down the stairway uncontrolled. Similarly, thestair-engaging portion or portions may have a length sufficient toensure that the stair-engaging portion is capable of simultaneouslyengaging the edges of at least three sequential steps of arepresentative stairway, such as a stairway of maximum-anticipated stepspacing. This ensures that during a stairway ascent or descent, thestair-engaging portion or portions are always positioned over the edgesof at least two steps, thus limiting potentially-unwanted forward orbackward rocking of the stair chair and motorized sled as an ascent ordescent is occurring.

At least some embodiments of the motorized sled are adapted to bereversibly attachable to the stair chair, so as to permit the sled to beattached to and detached from the stair chair as desired. For example,the motorized sled may be attached to the stair chair for transport ofpatients, but removed for more-compact storage. As another example, themotorized sled may also be detached while an empty stair chair iscarried up one or more flights of stairs and the sled may be carriedseparately. This may be advantageous in a situation where multiplepeople are to be evacuated, and it is desired to minimize use of thepower supply of the sled to those times where powered ascent/descent isneeded. The separation of the stair chair and the sled permits thesledded stair chair to be separated into several lighter-weightcomponents.

The sled may also be foldable from a deployed position to a foldedposition to permit compact storage of the stair chair and attached sled.Therefore, at least one attachment point between the stair chair and thesled may include a movable attachment, such as a pivoting, bending, orfolding attachment. To support the sled at a proper angle with respectto the stair chair when in the deployed position, the sled may beattached to the stair chair at another location with a brace or otherstructure.

Therefore, the sled may be reversibly attached to the stair chair atseveral points. For example, the sled may include an attachmentmechanism for attaching a lower end of the sled to a stair chair. Theattachment mechanism may be any mechanism known in the art, includinghinges, quick-release attachments, pivoting attachment mechanisms,bolts, rivets, pins, etc. An upper attachment mechanism may attach anupper or middle portion of the sled to the stair chair in such a way asto maintain one or more desired angles of the sled with respect to thestair chair Such attachments may include single- or multi-positionlocking/folding bars, telescoping connections, systems including one ormore hydraulic/pneumatic elements, or any other mechanism known in theart.

Some embodiments, to further facilitate flexible use of the stair chairand sled, may permit detachment of all or a portion of the motorizedtrack from the sled. Such embodiments include at least twostair-engaging portions to ensure that the stair chair is supportedagainst unwanted side-to-side motions, unless at least a track of themotorized track remains attached to the sled. In some such embodimentswhere an on-board power supply (such as a battery) is provided, theon-board power supply is removable, but may still remain electricallyconnected to the motorized track. In other embodiments, the power supplyand a motor of the motorized track is removable. In still otherembodiments, the entire motorized track is removable, either as a unitor in various components. Removal of all or a portion of the motorizedtrack permits lightening of the stair chair for transport or otherpurposes, either while engaging in a power-assisted ascent or descent(power supply removed but still electrically connected) or whileengaging in an ascent or descent without any powered assist.

One embodiment of a sled 30 is depicted in FIGS. 2-4 attached to a stairchair 10. The stair chair 10 is substantially similar to the stair chair10 illustrated in FIG. 1. This use with an existing stair chair 10illustrates that embodiments of the sled 30 may be adapted for use withessentially any stair chair 10, including current and future stairchairs 10. Therefore, as the details of the stair chair 10 havepreviously been discussed, they are not specifically discussed withrespect to FIGS. 2-4. One end of the sled 30 may be attached to thestair chair 10 proximate the rear wheels 12 of the stair chair 10. Theattachment of the sled 30 to the stair chair 10 proximate the rearwheels 12 may be a hinged-type or pivot-type attachment, allowing thesled 30 to be rotated between a deployed, stair-engaging position and astowed (or folded) position proximate the back 22 of the stair chair 10.In either position, the sled does not interfere with the use of thebearings on the stair chair so that the mechanism for transporting thestair chair may be quickly transitioned between the bearings and thesled.

Although not specifically illustrated in FIGS. 2-4, the sled 30 may havean additional attachment to the stair chair 10 that braces the sled 30when deployed and that controls the extent of deployment. The additionalattachment may be made to the stair chair frame 16 at a deployedattachment point 32 either previously-existing on the stair chair 10 orspecifically-attached to the stair chair 10 for this purpose. Thesupport extending between the attachment point 32 and the sled 30 is notshown in the Figures so as not to obscure the other features of the sled30, but it will be appreciated that a variety of braces, frames,supports, or other structures may be utilized to support the sled 30(and the stair chair 10 on the sled 30 when on stairs) in the deployedconfiguration. The sled 30 or the stair chair 10 may also have a stowedattachment point 34 that may reversibly engage a corresponding structure(on the stair chair 10 if the stowed attachment point 34 is on the sled30 and on the sled 30 if the stowed attachment point is on the stairchair 10) to secure the sled 30 in the stowed position. The stowedposition is shown in FIG. 4, while the deployed position is shown inFIGS. 2 and 3.

The sled 30 includes a track 36 and a rail or ski (“rail 38”). The track36 may include a track belt that is ribbed or includes a plurality ofteeth (and thereby form a toothed track belt), as discussed below withrespect to FIGS. 7-9, and is illustrated as a continuous looped trackbelt 50. In the embodiment of FIGS. 2-4, the track 36 is located on thesled 30 between two rails 38. In other embodiments, the track 36 may beplaced to one side of the sled 30, and a single rail 38 may be locatedon the other side of the sled 30. A single track 36 is shown in theillustrated embodiment because the weight of the rail 38 issubstantially less than the weight of the track 36. For example, in oneembodiment, the rail 38 is manufactured of extruded aluminum or the likeand is therefore very light weight. Additionally, the rail 38simultaneously forms part of a sled frame 40 of the sled 30, furtherreducing the total weight of the sled 30. In the embodiment of FIG. 2,one or more sled frame braces 42 extend between the rails 38 and thetrack 36, forming the remainder of the sled frame 40.

The track 36 is attached to the sled frame 40, and includes a drivemechanism or gear (“drive gear 44”) attached to a motor 46 and a pulley48, as best seen in FIGS. 3 and 4. The motor 46 may be a high-efficiencymotor and may be attached to the drive gear 44 by one or more gears,drive shafts, etc. as are known in the art. The motor 46 may be poweredby a battery or other portable power supply (not shown) that may beattached to the sled 30 or that may be electrically connected to themotor 46, such as by a cable, and that may be carried or worn by a userof the sled 30 and stair chair 10. Having the battery be carried or wornby the user may further reduce the total weight of the sled 30, whichmay allow for additional duty cycles before the battery must be replacedor recharged. The pulley 48 may include a tensioner to ensure that itscontinuous track belt 50 is properly tight and will not slip. Thevarious components and materials used for the track 36 may be chosen toreduce the total weight of the sled 30, such as by using aluminum andother light-weight materials where possible.

As discussed above, where there are two rails 38, the track 36 may becentrally located between the rails 38 and therefore inside the sledframe 40 formed by the two rails. The track 36 need not becentrally-located between the rails 38. Instead, the track 36 may belocated at any location between the rails 38, including immediatelyadjacent one of the rails 38. For example, the track 36 may be somewhatoffset from the exact center line between the rails 38, and this mayprovide additional room on one side of the track 36 for the motor 46,power supply (if any) and any associated gears or equipment to belocated on the sled 30 adjacent the track 36.

As may be best seen in FIG. 3, the rails 38 (in embodiments having morethan one rail 38) may have a bottom surface 52 that is substantiallyplanar over a majority of its length, and the bottom surface 52 of thetwo rails may be substantially co-planar. This bottom surface 52 mayinclude a low-friction high-durability surface to make the rails 38slide more easily up and down staircases/stairways. Examples of surfacesthat may be used include steel, ultra-high-molecular-weight polyethylene(UHMWPE), high-density polyethylene (HDPE), polyethylene treated withfluorine gas to form a surface layer of polyfluoroethylene (PFE), andpolytetrafluoroethylene (PTFE, commonly sold under the trademarkTeflon®). The foregoing are merely examples of low-friction,high-durability surfaces, and any such surface may be used in alternateembodiments of the invention. To further facilitate the rails 38 slidingup or down stairs, one or more of the ends of the bottom surfaces 52 mayinclude an upturn 54 or upturned portion. The upturn 54 causes a leadingportion of the rails 38 to be elevated in relation to the lower plane ofthe rails 38, allowing the rails 38 to more-easily engage subsequentsteps of a staircase, especially in situations where the spacing of thesteps is unequal.

As may also be seen in FIG. 3, a portion of the track 36 extends belowthe co-planar plane of the rails 38 so as to be able to engage the stepsof the staircase. The portion of the track 36 extending below theco-planar plane of the rails 38 may extend below the co-planar plane ofthe rails 38 a distance between approximately 0.5″ and 0.7″ (betweenapproximately 13 mm and 18 mm) in some embodiments. In still otherembodiments, the portion of the track 36 may extend below the rails 38 adistance of approximately 0.6″ (approximately 15 mm).

Track belt 50 may be smooth-surfaced, but some embodiments of the trackbelt 50 include ribs or teeth to more securely engage the steps. Suchembodiments may include very durable and harder materials, while thesmooth-surfaced track belts may include softer materials that permit thecontour of the steps to deform the track surface so that the tracksurface more securely engages the steps. In embodiments where the trackbelt 50 includes a ribbed or toothed track, the valleys of the trackbelt may lie close to (e.g. slightly above or slightly below) or withinthe co-planar plane of the rails 38 (while on the flat lower portion ofthe track belt), while the protruding portions of the track belt 50 maylie substantially below the co-planar plane of the rails 38 to securelyengage the steps.

The amount of the projection of the track 36 below the co-planar planeof the rails 38 may be varied to best engage the stairs, and mayapproximately match the height of the teeth of the track belt 50 (intoothed or ribbed embodiments), as will be set forth in more detailbelow with respect to FIGS. 7-9. To ensure that the track 36 securelyengages the steps throughout the ascent or descent, the continuous trackbelt of the track 36 may be backed by a slider, which may be formed, forexample, from a block of a low-friction and hard material that keeps theflat portion of the track belt flat even while the track 36 is restingon the corners of one or more steps. The slider also helps reduce thefriction of the rotating track belt 50, allowing the sled 30 toraise/lower more weight than otherwise possible. The slider may includematerials similar to the materials used for the bottom surface 52,including UHMWPE, HDPE, PFE, and PTFE. The width of the track 36 may bevaried as desired to achieve desired strength and/or weightcharacteristics for the track 36 and the sled 30. It is currentlyenvisioned that the track belt width may include widths of between lessthan 1″ to more than 6″ (less than 2.5 cm to more than 15 cm).

To keep the total weight of the sled 30 minimal, the length of the track36 may be limited to an amount sufficient to ensure that the track 36always engages at least one step. In other words, the length of thetrack 36 may be limited to an amount sufficient to at least span twosteps on a stairway having a maximum step spacing, plus some additionalsmall amount of length for safety. This may be seen with respect to FIG.5, which illustrates in schematic form the sled 36 on a section ofstairs. As may be seen in FIG. 5, a length 56 of the flat portion of thetrack 36 is slightly longer than a step-to-step spacing 58 of the stepsbetween a first step 64 and a second step 66. This ensures that thetrack 36 securely engages the upper step before releasing the lower stepor vice-versa.

As the track 36 may be limited in length in some embodiments as setforth above, it will be appreciated that at some points in time, thetrack 36 may only be engaging a single step. This is illustrated in FIG.6. If the limited-length track 36 were the only feature of the sled 30touching or engaging the steps, the sled 30 might become unstable and beprone to tipping either up or down. However, the rail 38 or rails 38have a length somewhat longer than the track 36, thereby providingadditional stability to the sled 30 and thereby to the stair chair 10.Specifically, the rail 38 or rails 38 may have a length sufficient toalways span at least two steps. In other words, the length of the rail38 or rails 38 may be sufficient to at least span the corners of threesteps on a stairway having the maximum step spacing, plus someadditional small amount of length.

This may be appreciated with respect to FIG. 5. In FIG. 5, a length 60of the rail 38 is at least slightly longer than a step-to-step spacing62 between the first step 64 and a third step 68. With this length 60,the rail 38 will never be over fewer than two steps, and the user of thesled 30 and attached stair chair 10 can ensure stability of theascending or descending stair chair 10 and sled 30 by pulling backsomewhat on the top of the back 22 of the stair chair 10, such as at thehandles 26 of the back 22. FIG. 6 illustrates how the rail 38 alwaysengages at least two steps and also makes clear how a user applying aforce at the back 22 in the direction of the stairs can keep the rail 38in contact with at least two stairs, even when the track 36 is only incontact with one stair.

Reference to FIG. 6 will also illustrate how an embodiment of the sled30 having a single rail 38 on one side and a single track 36 on theother side can remain stable during an ascent or descent of a flight ofstairs. The track 36 always contacts at least one step on one side ofthe sled 30, while the rail 38 always contacts at least two steps on theother side of the sled 30. The rail 38 provides front-to-back stability,while the rail 38 and track 36 provide side-to-side stability. A user ofa one-track-one-rail sled 30 may need to apply some sideways force tothe stair chair 10 to compensate for the fact that the motorized track36 applies stair climbing force exclusively on one side of the sled 30in such embodiments, but it is anticipated that such embodiments mayprovide further alternatives for reducing the weight of the sled 30.

As discussed above, some embodiments of the track belt 50 may be ribbedto improve security of the track 30 when ascending or descendingirregular surfaces such as stairs. One embodiment of a continuous trackbelt 756 for use with the track 30 is illustrated in more detail inFIGS. 7-11. FIGS. 7-11 illustrate a section of the continuous track belt756 used with the track 30. As may be seen by reference to FIG. 5,embodiments of the continuous track belt 756 form a loop around thedrive gear 44 and pulley 48. The drive gear 44 is connected to the motor46 and associated drive unit and provides power to the continuous trackbelt 756. As discussed above, along the remainder of its length, thecontinuous track belt 756 may ride along a low-friction slider that maybe manufactured of a plastic such as UHMWPE, HDPE, or LDPE. Use of thelow-friction slider has been found to improve efficiency of the track30, allowing the sled 30 to lift approximately 60% more weight upinclined surfaces such as stairways.

Returning now to FIG. 7, the Figure shows a plan view of a small sectionof the continuous track belt 756, showing one embodiment of therepeating profile of the continuous track belt 756. The illustratedsection shown is from the bottom, surface-contacting portion of thecontinuous track belt 756, so the surface of the continuous track belt756 that contacts the stairway or ground is downward in FIG. 7. Thecontinuous track belt 756 shown has three layers: a tread layer 764, afiber layer 766, and a drive layer 768. As shown in FIG. 7, the treadlayer 764 and the drive layer 768 have teeth or ribs 770 and teeth orribs 772, respectively. The teeth or ribs 770 of the tread layer 764engage stairs or other irregular surfaces being ascended or descendedfor security. The teeth or ribs 770 may have a flattened top 774 toreduce wear by preventing a sharp-peaked top from being irregularly tornduring use. The teeth or ribs 772 of the drive layer 768 engage thedrive gear 44 to transfer power from the motor 46 and drive unit to thecontinuous track belt 756. The teeth or ribs 772 may also engage achannel or guide in the drive gear 44, pulley 48, and/or slider to keepthe continuous track belt 756 properly aligned during use, as may beappreciated by reference to FIGS. 8 and 9, that show an embodiment of achannel 776 in the continuous track belt 756.

The tread layer 764 and the drive layer 768 may be manufactured frommaterials such as neoprene, urethane, rubber, and the like. In someembodiments, the tread layer 764 may have a durometer of betweenapproximately 60 A and 70 A and in some embodiments a durometer ofapproximately 70 A to provide softness and improved wear of thecontinuous track belt 756. This hardness of the tread layer 764 mayprovide an extremely long life during use and especially useful forascending or descending a large variety of stairway configurations. Thedrive layer 768 may have a higher durometer of between 80 A and 55 D orbetween 85 A to 95 A, and in some embodiments a durometer ofapproximately 90 A to maintain flexibility but provide tooth strengthfor interaction with the drive gear 758.

The fiber layer 766 provides strength to the continuous track belt 756and prevents undue expansion or stretching of the continuous track belt756 when loaded. The fiber layer 766 may include high-strength durablefibers such as steel fibers, polyesters, fiberglass, or long molecularchains of poly-paraphenylene terephthalamide produced from acondensation reaction between monomers of 1,4-phenylene-diamine(para-phenylenediamine) and terephthaloyl chloride, and commonly sold byE.I. du Pont de Nemours and Company as KEVLAR®. The fiber layer 766provides tensile strength to the continuous track belt 756 so that thecontinuous track belt 756 can withstand large tensile loads as the sled30 is used to ascend or descend stairways. By way of example, and notlimitation, the illustrated embodiment of the continuous track belt 756can withstand between 100 and 2,000 inch/lbs of torque.

By way of example and not limitation, one embodiment of the continuoustrack belt 756 will be illustrated with reference to FIG. 11 in specificdetail. It is anticipated that one or more of the measurements discussedherein may be modified and still fall within the scope of the presentinvention. In the illustrated embodiment, the continuous track belt 756may have a height of approximately 0.95″ to 1.16″ (24.1-29.5 mm) orbetween 1.05″ to 1.06″ (26.7-26.9 mm), as measured from the tip (i.e.the flattened top 774) of teeth or ribs 770 to the tip of teeth or ribs772. This height may be varied for reasons of weight or strength of thecontinuous track belt 756. The teeth or ribs 772 may have atooth-to-tooth spacing of approximately 0.28″ to 0.35″ (7.1-8.9 mm) or0.31″ to 0.32″ (7.9-8.1 mm) or of approximately 0.315″ (8 mm), and withsuch a spacing, the drive gear 44 and pulley 48 may have a diameter ofapproximately 4″ (100 mm). As may be appreciated by one of skill in theart, varying the size and spacing of the teeth or ribs 772 may permit orrequire varying the size of the drive gear 44 and pulley 48 accordingly.

The teeth or ribs 770 may have a tooth-to-tooth spacing of approximately1.51″ to 1.84″ (38.4-46.7 mm) or of 1.67″ to 1.68″ (42.4-42.7 mm), or ofapproximately 1.675″ (42.5 mm). The height of the teeth or ribs 770 froma valley 778 to the flat top 774 may be approximately 0.54″ to 0.66″(13.7-16.8 mm) or approximately 0.59″ to 0.61″ (15.0-15.5 mm) orapproximately 0.6″ (15.2 mm). These tooth-to-tooth spacings and teethheights have been found to function well at securely climbing and/ordescending a wide variety of stairway configurations, rises, runs, andstep spacings. The valley 778 of the teeth or ribs 770 may be providedwith a curve, and the radius of curvature of the valley 778 may beapproximately 0.22″ to 0.28″ (5.6-7.1 mm) or approximately 0.25″ (6.4mm). As indicated previously, the teeth or ribs 770 may be provided withthe flattened top 774 to reduce wear, and the flattened top 774 may havea width of approximately 0.17″ to 0.21″ (4.3-5.3 mm) or approximately0.19″ (4.8 mm).

Another embodiment of a sled 30 is depicted in FIGS. 12-15. In FIGS.12-13, the embodiment of the sled 30 is shown detached from the stairchair 10, while in FIGS. 14-15, the sled 30 is shown attached to thestair chair 10. In this embodiment, the sled 30 is readily separableinto at least two components: in FIGS. 12 and 14 all components areshown assembled/connected to each other, and in FIGS. 13 and 15, thesled is shown with a removable powered track 80 removed from the sled30. As the stair chair 10 is similar to the stair chairs 10 alreadydiscussed, and as the embodiment of the sled 30 depicted in FIGS. 12-15is intended to be usable with a wide variety of stair chairs 10, thedetails of the stair chair 10 are not discussed with respect to theseFigures.

In this embodiment of the sled 30, the rails 38 have been replaced by apair of elongate passive tracks 82 connected to each other by an uppertransverse support 84, as is most clearly illustrated in FIG. 13. Eachpassive track 82 includes a continuous looped track belt 86 supported byend pulleys 88 at each end. The end pulleys cause a lower surface of thecontinuous track belt 86 to bend upward on each end of the passivetracks 82, thus achieving an upturned end similar to the upturn 54 forease of engaging of subsequent steps as the sled 30 and stair chair 10move up or down a staircase. The passive tracks 82 may also be providedwith rollers, pulleys, or a low-friction surface just under thestair-contacting portion of the continuous tracks 84, so as to supportthe continuous tracks 84 as the edges of the steps move with respect tothe passive tracks 82. The continuous tracks 84 may be smooth-surfaced,or may be provided with teeth or ribs to engage the steps of thestairways. As the passive tracks 82 do not need to actively power thesled 30 and stair chair 10 up flights of stairs, some embodiments of thecontinuous tracks 84 of the passive tracks 82 have teeth or ribs havinga smaller profile than may be provided to the continuous track belt 50of the powered track 80, which may be essentially similar to thecontinuous track belt 50 discussed above in all regards and allspecifically-described or potential embodiments.

Many of the features and components of the powered track 80 may beessentially similar to the track 36 discussed above, with the exceptionthat the powered track 80 is made to be readily-removable from the sled30. For example, the powered track 80 may include the drive gear 44, themotor 46, the pulley 48, and the continuous track belt 50. Therefore,the extended discussion with relation to such features and embodimentsis not repeated at this point, but is instead incorporated by reference.In the illustrated embodiment, the powered track 80 (including, by wayof example only, the drive gear 44, the motor 46, the pulley 48, and thecontinuous track belt 50 as a unit) is removable mounted to the sled 30by way of a set of laterally extending supports 90 with mounting pins 94that are received in a pair of brackets or mounts 98 that are fixedlyattached, in the illustrated embodiment, to tracks 82. Additionally, thepowered track 80 is provided with a frame mount 92 formed by a pair ofbrackets, which are mounted to track 80 on one end and interconnected attheir distal ends by a transverse bar or cross piece 100. Supports 90pivotally mount the driven end of track 80 between tracks, with crosspiece 100 providing an engagement surface for a latch assembly, as morefully described below, for mounting the distal end of the powered track80 to the sled frame.

Each of the pins 94 is oriented to be received in a correspondingreceiving slot 96 of a respective mount 98, which mounts are mounted tothe inwardly facing sides of passive tracks 82. Cross piece 100 is thenengaged by latch assembly 102 attached to the upper transverse support84, which includes a recess to receive cross piece 100 and a latch tosecure to engage the cross piece in the recess when activated.

The illustrated mounting elements for mounting the powered track 80 tothe sled 30 have been provided taking into account the forces to beexperienced by the sled 30 and the powered track 80. For example, itwill be appreciated, that the powered track 80 should be secured againstdownward forces that would tend to separate it from the remainder of thesled 30. Therefore, latch assembly 102, the cross piece 100, and theframe mount 92 are designed and manufactured so as to be able to supportthe weight of the powered track belt 80 and all its components, whichmay include a power supply (not shown). However, the illustratedreceiving slot 96 is oriented differently, and is not designed tosupport the weight of the powered track 80. Instead, the receiving slot96 of the lower track mount 98 is oriented with its opening beinggenerally downward, with a solid portion of the lower track mount 98being oriented upward. This orientation provides strength to theconnection between the powered track 80 and the remainder of the sled 30as the stair chair 10 and sled 30 are in use. When the stair chair 10and sled 30 are ascending or descending a set of stairs, the weight ofthe patient or other person being transported is transferred from thestair chair 10 to the sled 30, and is directed generally downwardthrough the lower track mounts 98 through the connecting nubs 94 andthence to the powered track 80, which securely engages the stairs of thestairway. Therefore, the illustrated orientation of the lower trackmounts 98 provides strength to the connection between the sled 30 andthe powered track 80 during use.

Alternately, the track mounting components, that is the frame mount 92and the supports 90, may be spaced so that when cross-piece 100 isreceived by and latched to the latching assembly 102, pins 94 arealigned with the horizontal portion of the slot 96 so that bracket 98provides support to the track when in the sled is in the deployedposition. With this configuration, the distal end of the track is fixedby a pin connection to the frame (at the latching assembly) and theproximal, driven end of the track is supported by brackets 98 but withsome limited play in the slot. Moreover, with this the slotconfiguration—that is with the vertical legs and horizontal legs (asviewed for the orientation shown in FIG. 13), pins 94 can be easilymounted in the brackets through the vertical legs of the slots and thenmoved into the horizontal legs of the slots to thereby support thedriven end of the track while the other end of the track is then latchedto the frame to thereby secure the track to the frame. Once the latch isreleased, the pins can then be moved back in alignment with the verticallegs of the slots so that the pins and hence track can be disengagedfrom the sled frame.

One way of connecting/disconnecting the powered track 80 to theremainder of the sled 30 will now be described with reference to FIG.13. To mount the powered track 80 to the remainder of the sled 30 (whichmay be done with the sled 30 attached to the stair chair 10 or not), thepowered track 80 may be brought to a position relative to the remainderof the sled 30 such as illustrated in FIG. 13. The cross piece 100 ismaintained above and forward of the upper track mount 102, while thepowered track 80 is maneuvered to bring the pins 94 either in front ofand then below or behind and then below the lower track mounts 98.Alternatively, the powered track 80 may be rotated along its long axisso that the connecting pins 94 may pass between the lower track mountsand then un-rotated so that the connecting pins 94 are in alignment withand below the lower track mounts 98. Then, the powered track 80 isbrought upward (and slightly backward) so that the pins 94 enter intoand engage the receiving slots 96, and until pins 94 are fully seated inthe uppermost backmost portion of the receiving slots 96.

At this point, the powered track 80 is rotated around pins 94 until thecross piece 100 is engaged by latch assembly 102, which isclosed/locked/secured around the cross piece 100, thereby securing thepowered track 80 within the sled 30. Separation occurs by way of asubstantially reverse process. An alternative mounting/dismounting pathpasses the powered track 80 substantially from below the remainder ofthe sled 30, whereby the frame mount 92 passes between the passivetracks 82 forward of the upper spar 84, and then the connections aremade as described above.

It should be appreciated that various modifications of the connectionsbetween the powered track 80 and the remainder of the sled 30 may bemade. By way of example only, other mechanisms may be used to make theconnections between the powered track 80 and the remainder of the sled30. Pins or other structures similar to pins 94 may be provided on theinner sides of the passive tracks 82, and structures similar to mounts98 may be provided on the ends of supports 90. In such embodiments, itwill be appreciated that the orientation of the receiving slot 96 may bemodified. In other embodiments, instead of, or in addition to, a framemount 92, cross piece 100, and latch assembly 102, additional pins 90may be provided with attachment mechanisms for such mounts.

Other connection mechanisms may be provided other than thosespecifically illustrated, such as quick-release mechanisms, rotatinglocks, spring-loaded latches, or any other readily-reversible connectionknown in the art. Additionally, although the illustrated embodiment hasbeen shown with respect to removing the powered track 80 as a singleunit, other embodiments are envisioned whereby one or more components ofthe powered track 80 may be separately removable. For example, a powersupply can be removed separately in some embodiments, a motor unit canbe removed separately in some embodiments, and in some embodiments, apower supply/motor unit can be removed separately from a track portion.

Removal of one or more portions of the sled 30 permits use of alighter-weight configuration when such a lighter-weight configuration isdesired. For example, in an evacuation situation where the stair chair10 and attached sled 30 are to be used repeatedly over a short timeperiod, it may not be feasible to recharge a power supply (e.g. battery)of the sled 30. Therefore, it may be desirable to use the stair chair 10and sled 30 in a powered sense only when necessary or absolutelynecessary, such as when ascending or descending stairs with heavypassengers. When the stair chair 10 and sled 30 are being used withlighter passengers or when the stair chair 10 and sled 30 are beingreturned to a desired starting point unloaded, a removable portion ofthe sled 30 (which may include the entire sled 30, the entire poweredtrack 80, a power supply (not shown), or some other removable portion orcombination of portions) may be removed and carried separately. Toprovide more control over stairway descents when, for example, thepowered track 80 is removed, one or more of the passive tracks 82 may beprovided with a braking system that may be operable from a handle of thestair chair 10.

It should be noted that FIGS. 12-15 illustrate a readily-detachablepowered track 80 in conjunction with a pair of passive tracks 82. As itis envisioned that the stair chair 10 may be used for stairway descents(and possibly ascents) without the powered track 80 attached to the sled30, it is anticipated that at least two passive tracks 82 will bedesired for maximum stability of the stair chair 10. However, it isenvisioned that it would be possible to have only a single passive track82, or to have only a single passive track 82 of the illustrated lengthand to provide a shorter passive track 82 on the other side.Additionally, it is envisioned that one or more passive tracks 82 may beused in conjunction with embodiments not having a readily-removablepowered track 80, and that one or more passive tracks 82 (with orwithout braking systems) may be used in conjunction with the rail 38(such as with the rail 38 on one side and the passive track 82 on theother side) in both separable and non-separable embodiments.

As mentioned previously, the entire sled 30 may be removable, and mayalso be foldable with respect to the stair chair 10. Features of thesled 30 are illustrated in FIGS. 12-15 with respect to such folding andremoval. The sled 30 includes a pair of lower attachment structures 104and a pair of upper attachment structures 106 attached to the passivetracks 82. The lower attachment structures are configured for hinged orrotational attachment proximate the rear wheels 12 of the stair chair10. In removable-sled embodiments, the attachment is readily-reversible.The hinged or rotational attachment permits folding of the sled 30approximately against the back 22 of the stair chair 10 as previouslydiscussed.

The upper attachment structures are attached to the stair chair 10 atthe deployed attachment points 32, as previously discussed. FIGS. 14 and15 illustrate one mechanism for such attachment, namely a folding arm108. Folding arm 108 includes at least two arm portions that are joinedat their respective distal ends by a hinged joint, which when tightenedfixes the relative position of the two arm portions. The proximal endsof the respective arm portions are mounted to the stair chair frame 16by a bracket 32 and to one of the tracks by a pin connection mount. Inthis manner, the folding arm 108 is selectively lockable in at least twopositions (fully-folded and fully-deployed) to thereby secure the sled30 in the folded and deployed positions. Where additional lockablepositions of the folding arm 108 are provided, such positions may permituse of the sled at varying angles for passenger comfort, varyingstairway steepness, or any other reasons. Although only one folding arm108 is illustrated in FIGS. 14 and 15 for clarity, it should beunderstood that folding arms 108 may be provided on each side betweenthe stair chair 10 and the sled 30. The structures illustrated in theFigures are in all respects intended to be illustrative and notlimiting, and reference should be made to the claims to determine thescope of the claimed invention.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims, rather than by the foregoing description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

1. A sled for attachment to a stair chair including first and secondrear wheels, the sled comprising: a motorized track configured to engagea staircase; and first and second elongate stair-engaging portionsspaced outwardly of the motorized track and configured to contact thestaircase while the motorized track is engaging the staircase, the firstand second elongate stair-engaging portions being pivotably attachableto the stair chair proximate the stair chair rear wheels; the motorizedtrack being separately attachable to and detachable from the first andsecond elongate stair-engaging portions when the first and secondelongate stair-engaging portions is pivotably attached to the stairchair, wherein the motorized track and the first and second elongatestair-engaging portions are pivotable in unison from a generally uprightstowed position to a deployed position for engagement with thestaircase.
 2. The sled according to claim 1, wherein the first andsecond elongate stair-engaging portions have long axes disposedsubstantially parallel to each other and substantially parallel to along axis of the motorized track on opposite sides of the motorizedtrack.
 3. The sled according to claim 1, wherein the first and secondelongate stair-engaging portions include first and second passive belts.4. The sled according to claim 3, wherein the first and second passivebelts include teeth for engaging the staircase.
 5. The sled according toclaim 1, wherein the motorized track is centrally located between thefirst and second elongate stair-engaging portions.
 6. The sled accordingto claim 1, further including an upper transverse support extendingbetween the first and second elongate stair-engaging portions, themotorized track being attachable to the upper transverse support.
 7. Thesled according to claim 1, wherein the motorized track includes a motorand a continuous track belt that is driven by the motor.
 8. The sledaccording to claim 1, wherein the motorized track includes first andsecond laterally extending supports for engagement with the first andsecond elongate stair-engaging portions.
 9. The sled according to claim1, wherein the first and second elongate stair-engaging portions includefirst and second rails.
 10. A sled for attachment to a stair chairincluding first and second rear wheels, the sled comprising: first andsecond passive tracks being adapted to pivotably couple to the stairchair proximate the stair chair rear wheels and being movable from astowed position to a deployed position angled rearwardly of the stowedposition when mounted to the stair chair, the first and second passivetracks each including a continuous belt to simultaneously engage aplurality of steps of a staircase in the deployed position; and amotorized track positioned between the first and second passive tracks,the motorized track being separately attachable to and detachable fromthe first and second passive tracks, wherein the motorized track isremovable from the first and second passive tracks when the first andsecond passive tracks are pivotably coupled to the stair chair, andwherein the motorized track is pivotable in unison with the first andsecond passive tracks as the first and second passive tracks transitionfrom the stowed position to the deployed position for engagement withthe plurality of steps of the staircase.
 11. The sled according to claim10, wherein the motorized track is centrally located between the firstand second passive tracks.
 12. The sled according to claim 10, furtherincluding an upper transverse support extending between the first andsecond passive tracks, the motorized track being attachable to the uppertransverse support.
 13. The sled according to claim 10, wherein themotorized track includes a motor and a continuous track belt that isdriven by the motor.
 14. The sled according to claim 10, wherein themotorized track includes first and second laterally extending supportsfor engagement with the first and second passive tracks.
 15. The sledaccording to claim 10, wherein the first and second passive tracks eachinclude a continuous looped track belt.
 16. A method for operating astair chair including first and second passive tracks pivotably coupledto the stair chair, the method comprising: attaching a motorized trackto the first and second passive tracks, the motorized track including acontinuous belt configured to simultaneously engage a plurality steps ofa staircase; rotating the motorized track and the first and secondpassive tracks in unison from a stowed position to a deployed positionfor engagement with the plurality of steps of the staircase; recliningthe stair chair until the continuous belt of the motorized track engagesat least one of the plurality of steps of the staircase; activating themotorized track to move the stair chair along the plurality of steps ofthe staircase; and removing the motorized track from the stair chairwhile the first and second passive tracks remain attached to the stairchair.
 17. The method according to claim 16, further comprising rotatingthe first and second passive tracks from the deployed position to thestowed position.
 18. The method according to claim 16, wherein themotorized track is centrally located between the first and secondpassive tracks.
 19. The method according to claim 16, wherein themotorized track includes a motor to drive the continuous belt.
 20. Themethod according to claim 16, wherein the first and second passivetracks each include a continuous looped track belt.